A ‘great conjunction’ is when Jupiter and Saturn come so close together in the sky that, to the naked eye, they appear as one bright planet. It happens around once every 20 years, and this year’s great conjunction is even more special than usual, as the planets will appear closer together than they have since 1623. In reality, of course, Jupiter and Saturn aren’t that close – it’s a trick of perspective caused by their alignment as they orbit around the Sun.


When can you see the great conjunction in the UK?

To see the planets align, look above the southwestern horizon on 21 December after sunset, at around 5pm. The planets will only be visible for about an hour before they set in the west, so remember to look as soon as darkness falls. If you miss the conjunction, don’t worry: although the planets get closest on 21 December, you’ll have a great view of the pair on any evening in December, looking southwest after sunset.

Graphic showing Jupiter and Saturn close together in the sky © Pete Lawrence
© Pete Lawrence

This month’s astronomical event has some links to Christmas, too. In 1603, the astronomer Johannes Kepler calculated that, in the year 7 BC, there was a ‘triple conjunction’ between Jupiter and Saturn, in which the two planets met each other three times within around six months.

He suggested that this rare event could have been the Star of Bethlehem, which, in the Bible, guided the wise men on their journey to Jesus. However, more recent calculations show the planets were likely too far apart in the sky to appear as one bright star.

Whether or not you believe the story of the journey and the star, the great conjunction of Jupiter and Saturn is one not to miss. If you have binoculars, you’ll be able to see them as two separate planets, and if your binoculars are powerful enough, you might even be able to make out Saturn’s rings.

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Looking for stargazing tips? Check out our complete astronomy for beginners UK guide.


Abigail is a science journalist, based in Leeds.